Generally, in apparatuses in which relative motion is performed by using a frictional force in a state in which a plurality of apparatuses, such as a wheel member of a railway vehicle and a rail portion of a railway infrastructure, are in contact with each other, movements thereof can be accurately controlled when a frictional force which is greater than or equal to a predetermined value is secured.
Particularly, to stable drive a railway vehicle, an adhesion coefficient, which is a friction coefficient between a wheel member and a rail portion, has to be maintained to be greater than or equal to a predetermined value to secure a driving force, a braking force, and the like greater than or equal to predetermined levels.
However, since a conventional railway vehicle has a low adhesion coefficient between a wheel member and a rail portion, running performance, braking performance, and the like are lowered. Particularly, in the case in which the railway vehicle runs on a downwardly inclined section, slippage occurs, and thus there is a problem in that a braking distance is increased.
To reduce noise, wear, and friction energy between the wheel member and the rail portion, the adhesion coefficient, which is the friction coefficient between the wheel member and the rail portion, has to be within a predetermined range, and a positive friction state in which the friction coefficient increases even when a relative speed between the wheel member and the rail portion increases has to be maintained.
Conventionally, although a friction modifier has been applied to the wheel member and the rail portion such that the adhesion coefficient is within the predetermined range and the positive friction state is maintained, there have been problems in that the effect of the friction modifier is maintained only for a short period and an additional apparatus for applying the friction modifier has to be installed, and thus there is a need for reducing the problems.